1. The Field of the Invention
The present invention relates to a safety device used particularly in motor vehicles which, upon the onset of a collision, deploys an inflatable restraint cushion, known as an air bag cushion, to protect the occupants of the vehicle from the impact of a collision. More particularly, this invention relates to an attachment assembly for mounting an inflator assembly to a base plate.
2. The Relevant Technology
An inflatable vehicle occupant restraint, such as an air bag system with an inflatable air bag cushion, is inflated to protect an occupant of a vehicle upon the occurrence of a vehicle collision. When the vehicle, usually an automobile, is involved, in a collision, a crash signal actuates an inflator assembly of the air bag system to cause an air bag cushion to deploy. Typically, an actuator triggers a chemical, pyrotechnic, or some other reaction in the inflator assembly. The inflator assembly then emits an inflation fluid or gas which is directed to flow into the air bag cushion. The inflation fluid or gas inflates the air bag cushion from an uninflated condition to an inflated condition in which the air bag cushion extends into the vehicle occupant compartment. When the air bag cushion is in the inflated condition, it restrains an occupant of the vehicle from forcefully striking components of the vehicle as a result of the collision.
Initially, air bag systems were positioned in the vehicle occupant compartment substantially in front of the occupant. Not every collision, however, occurs from the front. It is not uncommon for the collision to occur at an angle relative to the occupant or from the side. In an attempt to protect the occupant from collisions that may be from a direction other than the front, air bag systems are being positioned to protect the side of the vehicle occupant.
One difficulty encountered by an air bag system intended to protect the side of the vehicle occupant is that there is limited space available in which to install the air bag system. As a result, a side impact air bag system must be designed as small as possible. Typically, the air bag system is in modular form. In general, an air bag system, regardless of location, includes an air bag cushion, an inflator assembly, a base plate, and a cover. Within the module, there are various conventional methods for holding the inflator assembly in position to inflate the air bag cushion.
It is common to provide an air bag assembly in which the inflator is permanently connected to either a base plate or the container for the air bag cushion. In the alternative, the inflator assembly can be attached to the base plate using conventional attaching techniques such as riveting, welding and pressing fitting the inflator assembly to a structural member such as the base plate. As air bag systems have been reduced in size, however, particularly for the designs being used for side impact protection, mounting the inflator assembly to the base plate has become increasingly difficult. In part, the difficulty arises because of the decrease in size of the inflator assembly. In addition, the inflator assembly may have various configurations which add to the difficulty of attaching the inflator assembly. As the size of the air bag system has been reduced, one typical configuration for the inflator-assembly is an elongated and narrow cylindrical body.
Attaching the elongated and narrow cylinder-shaped inflator assembly to a base plate has presented a variety of manufacturing problems. In this configuration, it is very difficult to rivet the inflator assembly to the base plate. In addition, it is difficult to weld to a cylindrical-shaped object. Making a clean, defect free weld between a narrow round surface and a flat surface presents difficulty. Welds are also very problematic to inspect in this configuration of an inflator assembly with existing inspection techniques. As a result, an unacceptable probability exists that there may be defective welds that are not caught and as consequence may fail.
In addition to reducing the size of the air bag system, there has also been a movement to reduce the weight and cost of the air bag system itself. As a result, it is desirable to make as many of the components further of the air bag system out of plastic as possible. Unfortunately, the use of plastic components further limits the various types of manufacturing processes that can be utilized in assembling the air bag system. Often, metal attachment pieces must be included if it is desired to use a welding attachment technique.
Another concern is that the cylindrical-shaped inflator assembly must be capable of serving as a pressure vessel that contains the inflation fluid or gas that used inflate the air bag cushion. The United States Department of Transportation has regulations and there are generally accepted engineering standards with regard to pressure vessels. These standards and regulations do not recommend welding on the pressure vessel section.
Another problem that is presented as the size of the air bag system is reduced is that upon the inflator assembly being actuated, the pressurized and sometimes heated, inflation fluid may cause damage to the interior surface of the air bag cushion. This is particularly true in hybrid, pyrotechnic and even cold gas inflators which have a hot gas exiting the inflator during the first few milliseconds after actuation. The initial hot gas may result in the interior of the air bag cushion being scorched and even burned.